White wash for pm problem

I recently purchased white wash to deal with a pm problem I’ve been having, I’ve never used this product, does anyone know if I should be spraying the plant while my lights are on or if I should be doing it while the lights are off?

I'm sure people will disagree with me for whatever reason, but as long as it's not oil based and there's no flowers on the plant I've never had problems spraying in the day. Usually early morning before the sun is beating down, but I've sprayed mid day as well and never had problems. If it's oil based though you definitely want to spray when the girls are out of direct light or it will burn the plants. I've never heard of White Wash, what's the active ingredient? Are you indoors or out? What stage are the plants in?

1 Tablespoon of baking soda in 32 ounces of water. Mist liberally once a week or after rain if outside.